As mankind continues to develop around the world, the demand for energy rises. Most energy used to power machines and generate electricity is derived from fossil fuels, such as coal, natural gas or oil. These supplies are limited and their combustion causes atmospheric pollution and the production of Carbon Dioxide, which is suspected to accelerate the greenhouse effect and lead to global climate change. Some alternative approaches to produce energy include the harnessing of nuclear energy, wind, moving water (hydropower), geothermal energy or solar energy. Each of these alternative approaches has drawbacks. Nuclear power requires large capital investments and safety and waste disposal are concerns. Wind power is effective, but wind turbines require a windy site, often far away from grid connections and take up large footprints of land. Hydropower requires the construction of large, potentially environmentally harmful dams and the displacement of large volumes of flowing water. Geothermal power requires a source of energy that is relatively near the surface—a characteristic not common to a large portion of the Earth—and has the potential to disrupt the balance of forces that exist inside the Earth's crust. Solar is one of the cleanest and most available forms of renewable energy and it can be harnessed by direct conversion into electricity (solar photovoltaic) or by heating a working fluid (solar thermal).
Solar photovoltaic (PV) technology relies on the direct conversion of solar power into electricity through the photoelectric effect: solar radiation's quantized particles, or photons, impinging on semiconductor junctions may excite pairs of conduction electrons and valence holes. These charged particles travel through the junction and may be collected at electrically conductive electrodes to form an electric current in an external circuit.
Photovoltaic is one of the most promising technologies for producing electricity from renewable resources, for a number of reasons: 1. The photovoltaic effect in Si and other solid-state semiconductors is well understood and the technology fully validated; 2. PV power plants convert directly solar power into electrical power, have no moving parts and require low maintenance; 3. Solar radiation is quite predictable and is maximum during hours of peak electricity consumptions; and 4. The industry has been aggressively pursuing a performance improvement and cost reduction path similar to the Moore's law in semiconductor electronics, approaching the condition of market competitiveness with traditional energy resources in many parts of the world. In 2010, approximately 16 GW of solar photovoltaic were installed globally, over a 100% growth from global installations in 2009.
However, PV is still more expensive than traditional energy resources in most parts of the world: while economy of scale and low cost manufacturing will contribute to further reduce cost, technological innovation is needed to achieve market competitiveness more rapidly and on an economically sound and sustainable basis.
Applications exist where the value-added features of photovoltaic module technology would offset their cost premium and the market would readily accept it. For example, in the case of new rooftops, it is desirable to incorporate photovoltaic modules as roofing elements in a manner that would displace the cost of rooftop construction materials and reduce the installation time.